Bump actions/checkout from 3 to 4 in /.github/workflows (#151)

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/audit.yml

@@ -9,7 +9,7 @@ jobs:
   security_audit:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: rustsec/audit-check@v1.4.1
         with:
           token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/ci.yml

@@ -25,7 +25,7 @@ jobs:
     name: "Build, check, and test with all features"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: Swatinem/rust-cache@v2
         with:
           shared-key: "cargo-deps"
@@ -55,7 +55,7 @@ jobs:
             build_name: "Just serde" 
     name: "Build ${{ matrix.build_name }}"
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: Swatinem/rust-cache@v2
         with:
           shared-key: "cargo-deps"
@@ -66,7 +66,7 @@ jobs:
     name: "Build using MSRV (lib only)"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: Swatinem/rust-cache@v2
       - name: Install MSRV
         uses: actions-rs/toolchain@v1
@@ -79,7 +79,7 @@ jobs:
     name: "Check code formatting"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: Swatinem/rust-cache@v2
         with:
           cache-targets: false
@@ -96,7 +96,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: [ "build_first" ]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: Swatinem/rust-cache@v2
         with:
           shared-key: "cargo-deps"
@@ -115,7 +115,7 @@ jobs:
     runs-on: ubuntu-latest
     needs: [ "build_first" ]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: Swatinem/rust-cache@v2
         with:
           shared-key: "cargo-deps"

.github/workflows/labeler.yml

@@ -9,7 +9,7 @@ jobs:
       pull-requests: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: actions/labeler@v4
         with:
           repo-token: "${{ secrets.GITHUB_TOKEN }}"